Electromagnetic valve actuating system

ABSTRACT

An electromagnetic valve actuating system opens and closes intake and exhaust valves of an engine under electromagnetic forces generated by an electromagnet. A reciprocally movable magnetic pole (8a) is coupled to the stem end of an intake/exhaust valve (8). An upper fixed permanent magnet (3) confronts one end of the movable magnetic pole (8a) the direction in which it is reciprocally movable. The intake/exhaust valve is opened and closed under attractive and repelling forces acting between the movable magnetic pole (8a) and the upper fixed permanent magnet (3). Since the polarity of the movable magnetic pole can be changed depending on how the first coil (5), the second coil (6), and the third coil (7) are energized, the timing to open and close the intake/exhaust valve (8) can be varied depending on the operating condition of the engine (1).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electromagnetic valve actuatingsystem for opening and closing intake and exhaust valves of an engineunder electromagnetic forces generated by an electromagnet.

2. Description of the Related Art

Some conventional actuating systems for opening and closing intake andexhaust valves include a single camshaft which has cams to operate theintake and exhaust valves, the camshaft being disposed above orlaterally by an engine. The camshaft is connected to the crankshaft ofthe engine by a belt or the like, so that the camshaft can rotatesynchronously with the rotation of the engine. The valves have stemswhose ends are pressed by cam surfaces of the camshaft through a linkmechanism such as rocker arms or push rods. The intake and exhaustvalves are normally closed by springs, and can be opened when their stemends are pressed by the cam surfaces.

In an alternative actuating system, an intake camshaft having cams foracting on intake valves and an exhaust camshaft having cams for actingon exhaust valves are disposed above an engine. The intake and exhaustvalves are opened when the stem ends of the intake valves are directlypushed by the cam surfaces of the intake camshaft and the stem ends ofthe exhaust valves are directly pushed by the cam surfaces of theexhaust camshaft.

However, the above conventional actuating systems for opening andclosing intake and exhaust, valves have several problems. First, theconventional systems include camshafts and link mechanisms which must beadded to the engine, and this necessarily renders the engine large insize.

Secondly, since the camshafts and the link mechanisms are driven by theoutput shaft of the engine, the engine output power is partly consumeddue to the frictional resistance produced when the camshafts and thelink mechanisms are driven by the engine. As a result, the effectiveengine output power is reduced.

Finally, the timing with which the intake and exhaust valves are openedand closed cannot be altered during operation of the engine, but thevalve opening and closing timing is preset such that the engine operateswith high efficiency only when it rotates at a predetermined speed.Therefore, the engine output power and efficiency are lower when theengine rotates at a speed different from the predetermined speed.

To solve the above problems, there have been proposed valve actuatingsystems for opening and closing intake and exhaust valves underelectromagnetic forces from electromagnets, rather than with camshafts,as disclosed in Japanese Laid-Open Patent Publications Nos. 58-183805and 61-76713.

However, the coils of the electromagnets disclosed in the abovepublications must be supplied with large electric energy in order togenerate electromagnetic forces large enough to actuate the intake andexhaust valves. For this reason, the coils radiate a large amount ofheat. As the electromagnets are associated with a cooling unit having aconsiderable cooling capacity, the problem of the large engine sizestill remains unsolved.

SUMMARY OF THE INVENTION

In view of the aforesaid problems, it is an object of the presentinvention to provide an electromagnetic valve actuating system foropening and closing intake and exhaust valves of an engine underelectromagnetic forces from an electromagnet, rather than with acamshaft, the electromagnet being high in efficiency and output.

According to the present invention there is provided an electromagneticvalve actuating system in which a movable magnetic pole is coupled to anintake/exhaust valve. The movable magnetic pole has a first end and asecond end an is reciprocally movable with the valve. An upper fixedpermanent magnet confronts the first end of the movable magnetic pole. Afirst intermediate fixed magnetic pole, coupled to the upper fixedpermanent magnet, confronts the upper fixed permanent magnet. A seconddistal fixed magnetic pole, coupled to the upper fixed permanent magnet,is and capable of confronting the first end of the movable magnetic polewhen the valve is open. A distal fixed magnetic pole coupled to thesecond intermediate fixed magnetic pole confronts a side of the movablemagnetic pole. A first coil generates a magnetic flux passing throughthe first intermediate fixed magnetic pole, a second coil generate amagnetic flux passing through the second intermediate fixed magneticpole, and a third coil generates a magnetic flux passing through themovable magnetic pole.

The movable magnetic pole is attracted to the upper fixed permanentmagnet to keep the intake/exhaust valve closed. To open theintake/exhaust valve, a magnetic path is produced between the movablemagnetic pole and the second intermediate fixed magnetic pole,developing a repelling force acting between the upper fixed permanentmagnet and the movable magnetic pole. To close the intake/exhaust valve,the movable magnetic pole is attracted again by the upper fixedpermanent magnet.

The forces opening and closing the intake/exhaust valve are thereforerendered strong, and the actuating system may be reduced in size.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an electromagnetic valve actuatingsystem according to an embodiment of the present invention;

FIG. 2 is a perspective view showing a magnetic body and a valve invertical cross section;

FIGS. 3(a) through 3(d) are diagrams showing the flow of magnetic linesof force within the magnetic body; and

FIG. 4 is a diagram showing the relationship the crankshaft angle andthe valve lift.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present invention will hereinafter be described indetail with reference to the drawings.

FIG. 1 is a block diagram showing an actuating system according to anembodiment of the present invention, and FIG. 2 shows in cross-sectionalperspective an actuator of the actuating system.

In FIG. 1, an engine 1 has an output shaft, adjacent to which there isdisposed a rotation sensor 2 for detecting the rotational speed andphase of the output shaft and converting the detected speed and phaseinto a signal. The engine 1 has intake and exhaust ports which areopened and closed by intake and exhaust valves, respectively. Of theseintake and exhaust valves, the intake valve will mainly be describedbelow.

An intake valve 8 is made of a magnetic material. The intake valve 8 isaxially slidably supported by a valve guide 9. The intake valve 8 has astem end 8a made of a magnetic material. The stem end 8a is confrontedby a permanent magnet 3 which is connected to a central upper portion ofa magnetic body 4.

The magnetic body 4 has first intermediate fixed magnetic poles 4apositioned on the lefthand and righthand sides of the permanent magnet4, and second intermediate fixed magnetic poles 4b disposed below andconfronting the first intermediate fixed magnetic poles 4a.

First coils 5 are disposed around the first left and right intermediatefixed magnetic poles 4a, and second coils 6 are also disposed around thesecond intermediate fixed magnetic poles 4b. The magnetic body 4 furtherhas, in its lower portion, distal fixed magnetic poles 4d facing sidesof the intake valve 8, and a third coil 7 through which the intake valve8 is movable as a core.

The rotation sensor 2, the first coils 5, the second coils 6, and thethird coil 7 are electrically connected to a control unit 12 by aninput/output interface 12d. The control unit 12 includes, theinput/output interface 12d which transmits output signals and receivesan input signal, a ROM 12b for storing a program and data, a CPU 12a foreffecting arithmetic operations under the control of the program storedin the ROM 12b, a RAM 12c for temporarily storing the input signals andthe results of arithmetic operations, and a control memory 12e forcontrolling the flow of signals in the control unit 12.

Operation of the electromagnetic valve actuating system according to thepresent invention will be described below. FIGS. 3(a) through 3(d) showthe flow of magnetic lines of force in the magnetic body 4. FIG. 3(a)shows the flow of magnetic lines of force when the valve is to beclosed, FIG. 3(b) shows the flow of magnetic lines of force when thevalve starts being opened from the closed condition, FIG. 3(c) shows theflow of magnetic lines of force when the valve remains open, and FIG.3(d) shows the flow of magnetic lines of force when the valve startsbeing closed from the open condition.

In FIG. 3(a), the third coil 7 is energized to generate downwardmagnetic lines of force in the stem of the intake valve 8. The generatedmagnetic lines of force flow from the stem of the intake valve 8 to thedistal fixed magnetic poles 4d and then through bypasses 4c to thepermanent magnet 3.

Since the direction of the magnetic lines of force of the permanentmagnet 3 is the same as the direction of the magnetic lines of forcegenerated by the third coil 7, these magnetic lines of force arecombined with each other, and flow through a magnetic path which extendsfrom the stem end 8a of the intake valve 8 through the stem thereof backagain to the distal fixed magnetic poles 4d.

When the magnetic lines of force flow from the permanent magnetic pole 3to the stem end 8a, an S (south) pole is created on the stem end 8a.Therefore, attractive forces are produced between the N (north) pole ofthe permanent magnet 3 which faces the stem end 8a, pulling the intakevalve 8 upwardly. In the position in which the head of the intake valve8 contacts the valve seat, the intake valve 8 remains closed.

As shown in FIG. 3(b), when the crankshaft angle as detected by therotation sensor 2 reaches the timing to open the intake valve 8, thethird coil 7 is de-energized, and the second coils 6 are energized togenerate downward magnetic lines of force in the second intermediatefixed magnetic poles 4b. The generated magnetic lines of force flowthrough a magnetic path which extends from the second intermediate fixedmagnetic poles 4b to the distal fixed magnetic poles 4d, and then fromthe stem end 8a back to the second intermediate fixed magnetic poles 4b.

When the magnetic lines of force flow from the stem end 8a to the secondintermediate fixed magnetic poles 4b, an N pole is created on the stemend 8a and S poles are created on the second intermediate fixed magneticpoles 4b.

Therefore, attractive forces are produced between the stem end 8a andthe second intermediate fixed magnetic poles 4b, enabling the intakevalve 8 to start moving in the opening direction.

As shown in FIG. 3(c), the intake valve 8 moves in the opening directionto the extent that the stem end 8a and the left and right secondintermediate fixed magnetic poles 4b are lined up. In such an alignedcondition, the gap between the stem end 8a and the second intermediatefixed magnetic poles 4b is minimum, and the attractive forces aremaximum. Therefore, the speed at which the intake valve 8 moves in theopening direction is reduced, and the intake valve 8 is held in thecondition shown in FIG. 3(c).

As shown in FIG. 3(d), when the crankshaft angle as detected by therotation sensor 2 reaches the timing to close the intake valve 8, thesecond coils 6 are de-energized, and the first coils 5 are energized togenerate downward magnetic lines of force in the first intermediatefixed magnetic poles 4a. The direction of the magnetic lines of forcegenerated by the first coils 5 are the same as the direction of themagnetic lines of force generated by the permanent magnet 3, and thesemagnetic lines of force are combined and flow through the stem end 8a tothe intake valve 8.

The magnetic lines of force flowing toward the intake valve 8 passthrough a magnetic path extending through the distal fixed magneticpoles 4d and the bypasses 4c and branched to the first intermediatefixed magnetic poles 4a and the permanent magnet 3.

At this time, N poles are created on the face of the permanent magnet 3facing the stem end 8a and the left and right first intermediate fixedmagnetic poles 4a, and an S pole is created on the stem end 8a.Therefore, the intake valve 8 is attracted to the permanent magnet 3 andthe first intermediate fixed magnetic poles 4a, thus starting to move inthe closing direction.

Upon elapse of a first preset time from the timing to close the intakevalve 8, the condition (b) is reached, when only the second coils 6 areenergized. The intake valve 8 is now subjected to attractive forces, andits movement in the closing direction is decelerated. The intake valve 8is thus decelerated in order to lessen shocks imposed when the head ofthe intake valve 9 is seated on the valve seat.

Upon elapse of a second preset time which is longer than the firstpreset time, the condition shown in FIG. 3(a) is reached when only thethird coil 7 is energized to attract the intake valve 8 in the closingdirection, thus closing the intake port. The intake valve 8 remainsclosed until the crankshaft angle of the engine reaches the next openingtiming.

FIG. 4 shows a cam profile curve. The horizontal axis of the graphindicates the crankshaft angle of the engine, and the vertical axisindicates the valve lift which represents the distance by which theintake valve moves.

The curves in FIG. 4 show the manner in which the valve lift varies asthe crankshaft angle varies. The solid-line curve represents changes inthe valve lift in the actuating system according to the presentinvention. The broken-line curve represents changes in the valve lift inthe conventional cam-operated actuating system.

At a time I which is the timing to open the intake valve 8, the thirdcoil 7 is de energized, and the second coils 6 are energized to switchthe flow of magnetic lines of force from the condition shown in FIG.3(a) to the condition shown in FIG. 3(b). The intake valve 8 now movesin the opening direction, while being accelerated, to the position II inwhich the second intermediate fixed magnetic poles 4b and the stem end8a are lined up.

When the position II is reached, the intake valve 8 is immediatelystopped, and remains open until timing III to close the intake valve 8.

At the timing III, the flow of magnetic lines of force is switched fromthe condition shown in FIG. 3(c) to the condition shown in FIG. 3(d).Upon elapse IV of the first preset time, the flow of magnetic lines offorce is switched from the condition shown in FIG. 3(d) to the conditionshown in FIG. 3(b), decelerating the intake valve 8 in the closingdirection. Upon elapse V of the second preset time, the flow of magneticlines of force is switched from the condition shown in FIG. 3(b) to thecondition shown in FIG. 3(a). The intake valve 8 now remains closeduntil next opening timing.

As shown in FIG. 4, the total opening area (over time) of the intakeport, which is expressed as an area surrounded by the horizontal axisand the profile curve, is greater with the valve opening and closingoperation of the present invention than with the conventional valveopening and closing operation. Therefore, any resistance to intake airis reduced, allowing intake air to be introduced quickly.

The first and second preset times are determined as follows: A table ofpreset times and engine rotational speeds is stored in advance in theROM 12b, and a preset time corresponding to a certain engine rotationalspeed is determined from the table based on the engine rotational speed.

The ROM 12 may store a map of engine rotational speeds and valve openingand closing timing values I and III, so that the valve opening andclosing timing may be varied as the engine rotational speed varies.

Furthermore, an engine cylinder control process for increasing orreducing the number of engine cylinders that are in operation dependingon the rotational speed of the engine can be carried out.

The magnetically interrupted portions of the magnetic path, the distancebetween the distal fixed magnetic poles 4d and the intake valve 8 aresmall irrespective of whether the valve is opened or closed, and henceany leakage of magnetic lines of force from the magnetic path is small.Accordingly, the electromagnetic forces acting on the intake valve 8 isstrong, with the result that the efficiency with which theelectromagnetic forces are generated is increased, and the amount ofheat generated by the coils is reduced.

While the intake valve has been described above, the actuating system ofthe present invention is also applicable to the exhaust valve, which isomitted from illustration.

Although a certain preferred embodiment has been shown and described, itshould be understood that the present invention should not be limited tothe illustrated embodiment but many changes and modifications may bemade therein without departing from the scope of the appended claims.

As described above, the electromagnetic valve actuating system accordingto the present invention can be used as a system for actuating intakeand exhaust valves of an engine, and suitable for use with an enginewhich is required to vary the timing to open and close the intake andexhaust valves freely depending on changes in an operating conditionsuch as the engine rotational speed.

I claim:
 1. An electromagnetic valve actuating system for opening andclosing a valve, such as an intake and exhaust valve of an engine,comprising:a movable magnetic pole coupled to the valve having a firstand second end, said movable magnetic pole being mounted forreciprocating movement; an upper fixed permanent magnet confronting saidmovable magnetic pole; a first intermediate fixed magnetic pole coupledto said upper fixed permanent magnet and confronting said movablemagnetic pole; a second intermediate fixed magnetic pole coupled to saidupper fixed permanent magnet and confronting the end of said movablemagnetic pole when the valve is open; a distal fixed magnetic polecoupled to said second intermediate fixed magnetic pole and confrontinga side of said valve; a first coil for generating a magnetic fluxpassing through said first intermediate fixed magnetic pole; a secondcoil for generating a magnetic flux passing through said secondintermediate fixed magnetic pole; a third coil for generating a magneticflux passing through said movable magnetic pole; and energizationcontrol means for energizing said first, second, and third coils to openand close said valve.
 2. An electromagnetic valve actuating systemaccording to claim 1, wherein said valve is made of a magnetic material.3. An electromagnetic valve actuating system according to claim 1,wherein said energization control means applies a repelling force actingbetween said upper fixed permanent magnet and said movable magnetic polebefore said valve is seated, thereby lessening shocks produced when thevalve is seated.
 4. An electromagnetic valve actuating system accordingto claim 1, wherein the timing established by said energization controlmeans to open and close the valve is variable as the rotational speed ofthe engine varies.
 5. A valve control system in an engine, comprising:anelectromagnet having coils and having fixed magnetic poles including anupper fixed pole, a distal fixed pole, and first and second intermediatefixed poles; a valve having a magnetic stem end positioned in closeproximity to said electromagnet; and control means for controllingmovement of said valve by energizing and deenergizing the coils of saidelectromagnet at timings corresponding to a speed of the engine toattract the magnetic stem end to the upper fixed pole and firstintermediate fixed pole, and to the distal fixed pole and secondintermediate fixed pole, alternatively, to open and close said valve. 6.A valve control system according to claim 5, further comprising speeddetection means for detecting a speed of the engine, and wherein saidcontrol means comprises a control unit including an input/outputinterface connected to said electromagnets and said speed detectionmeans, a storage means for storing a table of the timings correspondingto different speeds of the engine, and a processor calculating thetimings based on the speed detected by said detection means.
 7. A valvecontrol system according to claim 6, wherein said valve is upwardly anddownwardly movable and is held open by energizing and deenergizing thecoils.
 8. A method of controlling a valve in an engine with anelectromagnet having coils and surrounding the valve and having upperfixed, distal fixed, first and second fixed intermediate magnetic poles,and with a permanent magnet provided above the valve, comprising thesteps of:(a) providing the valve with a magnetic stem end in closeproximity to the permanent magnet; (b) detecting the speed of theengine; (c) reading the speed of the engine into a computer; and (d)energizing and deenergizing the coils in the electromagnet to attractthe magnetic stem end to the upper fixed pole and first intermediatefixed pole, and to the distal fixed pole and second intermediate fixedpole, alternatively, to open and close said valve, to move the valveupwardly and downwardly and hold the valve open at timings correspondingto the speed of the engine.
 9. A method according to claim 8, whereinsaid energizing and deenergizing of the electromagnet in step (d) isperformed at timings read by the computer from a preset speed timingtable based on the speed.
 10. A method according to claim 9, whereinstep (d) includes the steps of:(d1) holding the valve closed byenergizing first coils of the coils to attract the magnetic stem end ofthe valve to the permanent magnet, (d2) opening the valve bydeenergizing the first coils and energizing second coils of the coils toattract the magnetic stem end to poles of the electromagnet, (d3)holding open the valve by continuing deenergization of the second coilsas in step (d2), and aligning the magnetic stem end with the poles, and(d4) closing the valve by deenergizing the second coils and energizingthird coils of the coils to attract the magnetic stem end to thepermanent magnet.